[USRP-users] Phase coherence problems using TVRX2

John Malsbury john.malsbury at ettus.com
Thu Jun 14 12:29:02 EDT 2012


Lukas,

I forgot to mention that we do have a new knowledge base up.  There is a 
document you'll find there that explains the requirements for a MIMO 
system that can be used for direction of arrival measurements.

I recommend taking a look: www.ettus.com/kb

Search "MIMO" if you can't find the document in the menus.

Cheers,
John Malsbury



On 06/13/2012 11:06 AM, Lucas Caldeira de Oliveira wrote:
> Hi,
>
> I'm working on a project that uses a linear array with four antennas 
> for direction of arrival measurement. In this scenario, 
> phase-coherency between each antenna is necessary.
>
> I'm using one USRP rev4.5 with two TVRX2 rev1.1. I found that a random 
> phase offset is occuring every time i execute the program. After LO 
> lock, the phase offset remains constant.
>
> Inside FPGA, the phase accumulator is the same for four DDCs. These 
> signals between the input of ADC and inside GNURadio are phase 
> coherent. This random phase offset is occuring inside TVRX2.
>
> I'm using the last version of UHD and GNURadio.
>
> Could you give us information about this problem? Is it possible to 
> achieve phase coherency between these signals? Is there any limitation 
> in TVRX2 about this?
>
> Thanks,
>
> Lucas
>
>
> _______________________________________________
> USRP-users mailing list
> USRP-users at lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com

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